JPS634792B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating material, and more particularly to a coating material having a specific backing layer and suitable for strongly forming a surface layer made of polytetrafluoroethylene on a base material. It's about materials.

Polytetrafluoroethylene (hereinafter sometimes abbreviated as PTFE) is a material that has various properties required as a coating material, such as chemical resistance, heat resistance, and non-adhesion, but on the other hand, it has poor adhesive properties when used as is. The disadvantage is that it is difficult to form a strong bond with the material.

Various attempts have been made to improve the adhesion between PTFE and the base material, and one proposed method is to provide a PTFE sheet with a backing layer made of glass fiber cloth and adhere it to the base material through this layer. (Special Publication No. 39-25288 or Special Publication No. 57-5180)
(Refer to the publication number, etc.)

However, when using known methods, PTFE
Various disadvantages due to vapor penetration and condensation through the layers were unavoidable. In other words, when the thickness of the PTFE layer is small, blistering occurs near the interface between the backing glass fiber cloth and the base material due to the condensation of vapor that has passed through the layer, which reduces the adhesive strength with the base material. The coating material was still unsatisfactory as a coating material, as the coating material had a significant decrease in coating properties and, in severe cases, peeling occurred. Therefore, a method is generally adopted in which the thickness of the PTFE layer is increased to reduce the amount of vapor permeation to the interface, but in this case, the flexibility or processability of the coating material layer is inevitably This reduces the available substrate shapes, limits the available substrate shapes, and increases the cost.
The disadvantage was that the amount of PTFE used increased, and furthermore, phenomena such as the destruction of the coating layer due to condensation within the PTFE layer were observed.

The inventors of the present invention have conducted extensive research based on the recognition of the above problems, and have found that by using a glass fiber cloth with a specific structure called roving cloth, the thickness of the PTFE layer can be reduced. However, the present inventors have made the surprising finding that the above-mentioned problems no longer occur, and have now completed the present invention.

Thus, the present invention was completed based on the above findings, and provides a coating material in which a glass fiber cloth is laminated to a polytetrafluoroethylene sheet via an adhesive layer made of a melt-formable perfluoropolymer. The present invention provides a novel covering material characterized in that the polytetrafluoroethylene sheet has a thickness of 0.2 to 1.5 mm, and the glass fiber cloth is a roving cloth.

In the present invention, the thickness of the PTFE sheet is 0.2
It is important that it is ~1.5 mm, preferably 0.3-1.3 mm. If it is smaller than this range,
There is a risk that it will break during handling and cause a hole to form.On the other hand, if it is too large, as mentioned above,
Restrictions on base material shape due to reduced workability, expensive
There are drawbacks such as an increase in the amount of PTFE used and furthermore, destruction of the coating layer itself, both of which are disadvantageous.

In the present invention, a PTFE sheet is laminated to a glass fiber cloth via an adhesive layer made of a melt-formable perfluoropolymer. By heating and melting this polymer, it adheres to the softened PTFE, and a portion of it also penetrates into the glass fiber layer, and when it cools and solidifies, it creates an anchor effect.
A strong bond between the PTFE/glass fiber cloth is achieved. Such polymers include various copolymers of tetrafluoroethylene (TFE) and perfluoroolefins and/or perfluoro(alkyl vinyl ethers), such as TFE-hexafluoropropylene (HFP) copolymers, TFE-perfluoro(propyl vinyl ether) (PPVE)
Copolymer, TFE-HFP-PPVE terpolymer,
TFE-perfluoro(propoxypropyl vinyl ether) (PHVE) copolymer, TFE-HFP-
A PHVE terpolymer or the like can be preferably employed.

Although the method for forming the adhesive layer as described above is not particularly limited, a method in which a perfluoropolymer film separately obtained by melt molding is placed between the PTFE sheet and the roving cloth and heated under pressure is preferable from the viewpoint of operability. Adoptable. In this case, the film thickness is too small.
This can cause poor adhesion between the PTFE and glass fiber cloth, and if it is too large, it may pass through the glass fiber cloth and cover the back side, causing poor adhesion between the glass fiber cloth and the base material. Therefore, it is preferable to select from a range of about 25 to 100 μm.

In the present invention, it is extremely important to use a roving sheet as the glass fiber cloth.
The roving sheet is made by weaving roving, that is, glass fibers (twist number of 0.1/25 mm or less) into a plain weave, in which several hundred or more continuous filaments are bundled without twisting. Conventionally, the backing materials for fluororesin sheets have been glass cloth made of twisted yarn, bag filter cloth,
Knitted fabrics and plaited fabrics have been used, and there are no known examples of using roving sheets.

In the present invention, by using the roving sheet, a discharge path for permeated steam is secured between the PTFE layer and the base material, so formation of blisters, peeling, etc. due to condensation and accumulation of permeated steam is suppressed, The durability of the coating layer is significantly improved. That is, in the roving sheet, since the strands are not twisted, the voids between the filaments extend as continuous holes in both the weft and warp directions.
If the amount of perfluoropolymer used as an adhesive medium between the PTFE sheet and the base material is appropriate, a discharge path will be secured. In addition, when using a relatively high-viscosity adhesive medium between the base material and the roving cloth, it is relatively difficult for the adhesive medium to penetrate between the filaments, so even if the amount is large, there will be no problem. Not.

On the other hand, when using conventional twisted yarn glass cloth, bag filter cloth, knitted fabric, braided fabric, etc., the adhesive medium between the PTFE sheet or the base material easily penetrates into the glass fiber cloth. Moreover, since the strands are twisted, the voids between the filaments are divided, resulting in various defects due to the condensation and accumulation of the permeated vapor as described above.

The roving cloth that can be suitably used in the present invention has a filament diameter of 10 to 25 μm, a roving with a number of 1000 to 10000 filaments, and a thickness of
Examples include those with a diameter of about 0.3 to 0.9 mm.

For the production of the coating material of the present invention, methods using a heated press, heated rolls, etc. used for the production of ordinary laminates can also be adopted, but the following methods can be preferably employed when producing long objects. It is. In other words, a perfluoropolymer film and roving cloth are layered in this order on one side of a PTFE sheet of a predetermined length, and a heat-resistant mold release material such as aluminum foil is placed below the roving cloth, and this is layered with a heat-conducting material such as a stainless steel tube. In this method, the material is wound around a steel core material, then wrapped with aluminum foil or the like several times to secure the ends, then wrapped with metal wire, etc., and then tightened and fixed, and then heated in a heating furnace at 330 to 380°C. In this case, in order to achieve sufficient bonding, it is preferable to apply a stretching force of about 0.1 to 3.0 kg/cm during winding, and the heating time is
Depending on the thickness, approximately 0.5 to 2.0 hours/cm is usually adopted.

The coating material of the present invention includes metals such as iron, aluminum, copper, or alloys thereof, such as stainless steel and brass, inorganic materials such as glass, cement, and concrete, FRP, polyethylene, polypropylene, and ethylene-vinyl acetate copolymer. Synthetic resins such as coalescence, acrylic resin, polyester, polyvinyl chloride, polyvinylidene chloride, polycarbonate,
It is possible to coat substrates made of various materials such as organic materials such as wood by appropriate means depending on the material. For example, when coating metal substrates, inorganic materials, and wood, there is a method using adhesives, and when coating thermoplastic synthetic resins, there is a method using melt adhesion.
When coating the thermosetting synthetic resin, it is preferable to use a method in which the resin is laminated with an uncured material and then heated and pressurized to achieve bonding at the same time as curing.

The coating material of the present invention is extremely useful as a lining material for piping and towers and tanks that handle permeable fluids,
Particularly when applied to FRP, in addition to the above-mentioned features, it also exhibits features such as lightness.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 PTFE sheets each having a width of 1 m (thickness
0.8mm), TFE-PPVE copolymer film (thickness
50μm) and roving cloth (filament diameter 15μm, number of filaments 2040) and aluminum foil with a width of 1.1m were stacked in this order, and while applying a stretching force of 2Kg/cm to the PTFE sheet, it was placed on a stainless steel pipe with an outer diameter of 25cm. Each was wound 30m. The thickness of the wound layer was approximately 4 cm. After wrapping only aluminum foil three more times for fixation, it was tied and fixed with stainless steel wire. Then, it was heated for 4 hours in an electric drying oven maintained at 340°C. After cooling, the binding was released and the aluminum foil was further removed to obtain a laminated sheet.

Cut out a part of the laminated sheet obtained above (30cm x
30cm), epoxy acrylate resin (made by Japan U-Pica: Neopol) on both sides of the roving cloth.
8250L), layered 10 sheets of chopped strand pine with a thickness of 0.3 mm, placed a glass flat plate on top with release paper, placed a 5 kg weight on it, and left it at room temperature for 16 hours. It was cured by heating at ℃ for 4 hours.

The peeling strength of the FRP molded body having the PTFE surface layer thus obtained (JIS-K-6744: peeling speed 50
mm/min) was 3.6Kg/cm. In addition, this molded body was attached to a Dupont steam diffusion type lining tester, and the PTFE side was exposed to boiling distilled water and the FRP side was exposed to boiling distilled water.
Each piece was kept in constant contact with cold water at 15°C for one month, but no change in appearance occurred, and no decrease in peel strength was observed.

Comparative Example 1 Instead of roving cloth, glass threads made by twisting 800 glass filaments with a diameter of 9 μm were used as warp threads.
A laminated sheet was formed in the same manner as in Example 1, except that a glass cloth woven in a twill weave was used as the weft, and an FRP molded body was obtained in the same manner. In this case, the peel strength was only 0.9 kg/cm, and in the lining test, blisters and white spots were observed, and the peel strength was only 0.9 kg/cm.
It decreased to 0.5Kg/cm.

Comparative Example 2 In Comparative Example 1, the diameter of the glass cloth was 7 μm.
Even when using a glass yarn made by twisting 900 glass filaments and weaving it into a plain weave, blisters and white spots were observed in the lining test, and the peel strength after the test was 0.9.
It was only Kg/cm.

Examples 2 and 3 As roving cloth, filament diameter 15μ
m, one with 10,000 filaments (Example 2),
When a filament with a diameter of 21 μm and a filament number of 1040 (Example 3) was used in the same manner as in Example 1, the initial peeling strength was 3.5 Kg/cm and 3.0 Kg/cm, respectively. No abnormality was observed in the lining test.

Claims (1)

[Claims] 1. A coating material formed by laminating a glass fiber cloth on a polytetrafluoroethylene sheet via an adhesive layer made of a melt-formable perfluoropolymer, wherein the polytetrafluoroethylene sheet has a thickness of 0.2 to 1.5 mm. , a covering material characterized in that the glass fiber cloth is a roping cloth.